2 * Copyright (C) 1995-2007 University of Karlsruhe. All right reserved.
4 * This file is part of libFirm.
6 * This file may be distributed and/or modified under the terms of the
7 * GNU General Public License version 2 as published by the Free Software
8 * Foundation and appearing in the file LICENSE.GPL included in the
9 * packaging of this file.
11 * Licensees holding valid libFirm Professional Edition licenses may use
12 * this file in accordance with the libFirm Commercial License.
13 * Agreement provided with the Software.
15 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
16 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * @brief Compute the strongly connected regions and build
23 * backedge/loop datastructures.
24 * A variation on the Tarjan algorithm. See also [Trapp:99],
26 * @author Goetz Lindenmaier
44 #include "irgraph_t.h"
52 /* A variant of the loop tree that avoids loops without head.
53 This reduces the depth of the loop tree. */
54 #define NO_LOOPS_WITHOUT_HEAD 1
56 static ir_graph *outermost_ir_graph; /* The outermost graph the scc is computed
58 static ir_loop *current_loop; /* Current loop construction is working
60 static int loop_node_cnt = 0; /* Counts the number of allocated loop nodes.
61 Each loop node gets a unique number.
62 What for? ev. remove. @@@ */
63 static int current_dfn = 1; /* Counter to generate depth first numbering
66 static int max_loop_depth = 0;
68 void link_to_reg_end (ir_node *n, void *env);
69 void set_projx_link(ir_node *cb_projx, ir_node *end_projx);
70 ir_node *get_projx_link(ir_node *cb_projx);
72 /**********************************************************************/
73 /* Node attributes **/
74 /**********************************************************************/
76 /**********************************************************************/
77 /* Node attributes needed for the construction. **/
78 /**********************************************************************/
80 typedef struct scc_info {
81 int in_stack; /**< Marks whether node is on the stack. */
82 int dfn; /**< Depth first search number. */
83 int uplink; /**< dfn number of ancestor. */
84 /* ir_loop *loop; *//* Refers to the containing loop. */
86 struct section *section;
92 static INLINE scc_info* new_scc_info(void) {
93 scc_info *info = obstack_alloc (outermost_ir_graph->obst, sizeof (scc_info));
94 memset (info, 0, sizeof (scc_info));
99 mark_irn_in_stack (ir_node *n) {
100 scc_info *scc = get_irn_link(n);
106 mark_irn_not_in_stack (ir_node *n) {
107 scc_info *scc = get_irn_link(n);
113 irn_is_in_stack (ir_node *n) {
114 scc_info *scc = get_irn_link(n);
116 return scc->in_stack;
120 set_irn_uplink (ir_node *n, int uplink) {
121 scc_info *scc = get_irn_link(n);
123 scc->uplink = uplink;
127 get_irn_uplink (ir_node *n) {
128 scc_info *scc = get_irn_link(n);
134 set_irn_dfn (ir_node *n, int dfn) {
135 scc_info *scc = get_irn_link(n);
141 get_irn_dfn (ir_node *n) {
142 scc_info *scc = get_irn_link(n);
149 set_irn_loop (ir_node *n, ir_loop *loop) {
153 /* Uses temporary information to get the loop */
154 ir_loop *(get_irn_loop)(const ir_node *n) {
155 return _get_irn_loop(n);
160 static ir_loop *find_nodes_loop (ir_node *n, ir_loop *l) {
164 /* Test whether n is contained in this loop. */
165 for (i = 0; i < get_loop_n_nodes(l); i++)
166 if (n == get_loop_node(l, i)) return l;
168 /* Is this a leave in the loop tree? If so loop not found. */
169 if (get_loop_n_sons(l) == 0) return NULL;
171 /* Else descend in the loop tree. */
172 for (i = 0; i < get_loop_n_sons(l); i++) {
173 res = find_nodes_loop(n, get_loop_son(l, i));
179 /* @@@ temporary implementation, costly!!! */
180 ir_loop * get_irn_loop(ir_node *n) {
181 ir_loop *l = get_irg_loop(current_ir_graph);
182 l = find_nodes_loop(n, l);
187 /**********************************************************************/
189 /**********************************************************************/
191 static ir_node **stack = NULL;
192 static int tos = 0; /* top of stack */
195 * initializes the stack
197 static INLINE void init_stack(void) {
199 ARR_RESIZE (ir_node *, stack, 1000);
201 stack = NEW_ARR_F (ir_node *, 1000);
207 static INLINE void free_stack(void) {
215 * push a node onto the stack
217 * @param n The node to push
222 if (tos == ARR_LEN (stack)) {
223 int nlen = ARR_LEN (stack) * 2;
224 ARR_RESIZE (ir_node *, stack, nlen);
227 mark_irn_in_stack(n);
231 * pop a node from the stack
233 * @return The topmost node
235 static INLINE ir_node *
238 ir_node *n = stack[--tos];
239 mark_irn_not_in_stack(n);
244 * The nodes up to n belong to the current loop.
245 * Removes them from the stack and adds them to the current loop.
248 pop_scc_to_loop (ir_node *n)
257 set_irn_dfn(m, loop_node_cnt);
258 add_loop_node(current_loop, m);
259 set_irn_loop(m, current_loop);
262 /* if (m==n) break;*/
265 /* i might be bigger than 1 for dead (and that's why bad) loops */
267 printf("Mehr als eine Iteration!!!!!!!!!!!!!!!!!!!!!!!!!!!!11111\n");
271 /* GL ??? my last son is my grandson??? Removes loops with no
272 ir_nodes in them. Such loops have only another loop as son. (Why
273 can't they have two loops as sons? Does it never get that far? ) */
274 static void close_loop (ir_loop *l)
276 int last = get_loop_n_elements(l) - 1;
277 loop_element lelement = get_loop_element(l, last);
278 ir_loop *last_son = lelement.son;
280 if (get_kind(last_son) == k_ir_loop &&
281 get_loop_n_elements(last_son) == 1) {
284 lelement = get_loop_element(last_son, 0);
287 if (get_kind(gson) == k_ir_loop) {
288 loop_element new_last_son;
290 gson->outer_loop = l;
291 new_last_son.son = gson;
292 l->children[last] = new_last_son;
299 /* Removes and unmarks all nodes up to n from the stack.
300 The nodes must be visited once more to assign them to a scc. */
302 pop_scc_unmark_visit (ir_node *n)
308 set_irn_visited(m, 0);
312 /**********************************************************************/
313 /* The loop datastructure. **/
314 /**********************************************************************/
316 /* Allocates a new loop as son of current_loop. Sets current_loop
317 to the new loop and returns the father. */
318 ir_loop *new_loop (void) {
319 ir_loop *father, *son;
321 father = current_loop;
323 son = (ir_loop *) obstack_alloc (outermost_ir_graph->obst, sizeof (ir_loop));
324 memset (son, 0, sizeof (ir_loop));
325 son->kind = k_ir_loop;
326 son->children = NEW_ARR_F (loop_element, 0);
330 son->outer_loop = father;
331 add_loop_son(father, son);
332 son->depth = father->depth+1;
333 if (son->depth > max_loop_depth) max_loop_depth = son->depth;
334 } else { /* The root loop */
335 son->outer_loop = son;
340 son->loop_nr = get_irp_new_node_nr();
349 /* Finishes the datastructures, copies the arrays to the obstack
351 A. Schoesser: Caution: loop -> sons is gone. */
352 static void mature_loop (ir_loop *loop) {
355 new_sons = NEW_ARR_D (ir_loop *, current_ir_graph->obst, ARR_LEN(loop->sons));
356 memcpy (new_sons, loop->sons, sizeof (ir_loop *) * ARR_LEN(loop->sons));
357 DEL_ARR_F(loop->sons);
358 loop->sons = new_sons;
362 /* Returns outer loop, itself if outermost. */
363 ir_loop *(get_loop_outer_loop)(const ir_loop *loop) {
364 return _get_loop_outer_loop(loop);
367 /* Returns nesting depth of this loop */
368 int (get_loop_depth)(const ir_loop *loop) {
369 return _get_loop_depth(loop);
372 /* Returns the number of inner loops */
373 int (get_loop_n_sons)(const ir_loop *loop) {
374 return _get_loop_n_sons(loop);
377 /* Returns the pos`th loop_node-child *
378 * TODO: This method isn`t very efficient ! *
379 * Returns NULL if there isn`t a pos`th loop_node */
380 ir_loop *get_loop_son (ir_loop *loop, int pos) {
381 int child_nr = 0, loop_nr = -1;
383 assert(loop && loop->kind == k_ir_loop);
384 while(child_nr < ARR_LEN(loop->children))
386 if(*(loop -> children[child_nr].kind) == k_ir_loop)
389 return(loop -> children[child_nr].son);
395 /* Use EXCLUSIVELY this function to add sons, otherwise the loop->n_sons
399 add_loop_son(ir_loop *loop, ir_loop *son) {
402 assert(loop && loop->kind == k_ir_loop);
403 assert(get_kind(son) == k_ir_loop);
404 ARR_APP1 (loop_element, loop->children, lson);
408 /* Returns the number of nodes in the loop */
409 int get_loop_n_nodes (ir_loop *loop) {
410 assert(loop); assert(loop->kind == k_ir_loop);
411 return loop -> n_nodes;
412 /* return ARR_LEN(loop->nodes); */
415 /* Returns the pos`th ir_node-child *
416 * TODO: This method isn`t very efficient ! *
417 * Returns NULL if there isn`t a pos`th ir_node */
418 ir_node *get_loop_node (ir_loop *loop, int pos) {
419 int child_nr, node_nr = -1;
421 assert(loop && loop->kind == k_ir_loop);
422 assert(pos < get_loop_n_nodes(loop));
424 for (child_nr = 0; child_nr < ARR_LEN(loop->children); child_nr++) {
425 if(*(loop -> children[child_nr].kind) == k_ir_node)
428 return(loop -> children[child_nr].node);
431 assert(0 && "no child at pos found");
435 /* Use EXCLUSIVELY this function to add nodes, otherwise the loop->n_nodes
439 add_loop_node(ir_loop *loop, ir_node *n) {
442 assert(loop && loop->kind == k_ir_loop);
443 assert(get_kind(n) == k_ir_node || get_kind(n) == k_ir_graph); /* used in callgraph.c */
444 ARR_APP1 (loop_element, loop->children, ln);
448 /* Returns the number of elements contained in loop. */
449 int get_loop_n_elements (const ir_loop *loop) {
450 assert(loop && loop->kind == k_ir_loop);
451 return(ARR_LEN(loop->children));
455 Returns the pos`th loop element.
456 This may be a loop_node or a ir_node. The caller of this function has
457 to check the *(loop_element.kind) field for "k_ir_node" or "k_ir_loop"
458 and then select the appropriate "loop_element.node" or "loop_element.son".
461 loop_element get_loop_element(const ir_loop *loop, int pos) {
462 assert(loop && loop->kind == k_ir_loop && pos < ARR_LEN(loop->children));
463 return(loop -> children[pos]);
466 int get_loop_element_pos(const ir_loop *loop, void *le) {
468 assert(loop && loop->kind == k_ir_loop);
470 n = get_loop_n_elements(loop);
471 for (i = 0; i < n; i++)
472 if (get_loop_element(loop, i).node == le) return i;
476 int get_loop_loop_nr(const ir_loop *loop) {
477 assert(loop && loop->kind == k_ir_loop);
479 return loop->loop_nr;
486 /** A field to connect additional information to a loop. Only valid
487 if libfirm_debug is set. */
488 void set_loop_link (ir_loop *loop, void *link) {
489 assert(loop && loop->kind == k_ir_loop);
494 void *get_loop_link (const ir_loop *loop) {
495 assert(loop && loop->kind == k_ir_loop);
503 int (is_ir_loop)(const void *thing) {
504 return _is_ir_loop(thing);
507 /* The outermost loop is remarked in the surrounding graph. */
508 void (set_irg_loop)(ir_graph *irg, ir_loop *loop) {
509 _set_irg_loop(irg, loop);
512 /* Returns the root loop info (if exists) for an irg. */
513 ir_loop *(get_irg_loop)(ir_graph *irg) {
514 return _get_irg_loop(irg);
518 /**********************************************************************/
519 /* Constructing and destructing the loop/backedge information. **/
520 /**********************************************************************/
522 /* Initialization steps. **********************************************/
525 init_node (ir_node *n, void *env) {
526 set_irn_link (n, new_scc_info());
531 init_scc_common (void) {
538 init_scc (ir_graph *irg) {
540 irg_walk_graph (irg, init_node, NULL, NULL);
542 irg_walk (irg, link_to_reg_end, NULL, NULL);
549 cg_walk (init_node, NULL, NULL);
551 #if EXPERIMENTAL_LOOP_TREE
552 cg_walk (link_to_reg_end, NULL, NULL);
556 /* Condition for breaking the recursion. */
557 static int is_outermost_Start(ir_node *n) {
558 /* Test whether this is the outermost Start node. If so
559 recursion must end. */
560 if ((get_irn_op(n) == op_Block) &&
561 (get_Block_n_cfgpreds(n) == 1) &&
562 (get_irn_op(skip_Proj(get_Block_cfgpred(n, 0))) == op_Start) &&
563 (get_nodes_block(skip_Proj(get_Block_cfgpred(n, 0))) == n)) {
567 /* @@@ Bad condition:
568 not possible in interprocedural view as outermost_graph is
569 not necessarily the only with a dead-end start block.
570 Besides current_ir_graph is not set properly. */
571 if ((get_irn_op(n) == op_Block) &&
572 (n == get_irg_start_block(current_ir_graph))) {
573 if ((!get_interprocedural_view()) ||
574 (current_ir_graph == outermost_ir_graph))
581 /* When to walk from nodes to blocks. Only for Control flow operations? */
583 get_start_index(ir_node *n) {
584 #undef BLOCK_BEFORE_NODE
585 #define BLOCK_BEFORE_NODE 1
587 #if BLOCK_BEFORE_NODE
589 /* This version assures, that all nodes are ordered absolutely. This allows
590 to undef all nodes in the heap analysis if the block is false, which means
592 I.e., with this code, the order on the loop tree is correct. But a (single)
593 test showed the loop tree is deeper. */
594 if (get_irn_op(n) == op_Phi ||
595 get_irn_op(n) == op_Block ||
596 (get_irn_op(n) == op_Filter && get_interprocedural_view()) ||
597 (get_irg_pinned(get_irn_irg(n)) == op_pin_state_floats &&
598 get_irn_pinned(n) == op_pin_state_floats))
599 // Here we could test for backedge at -1 which is illegal
606 /* This version causes deeper loop trees (at least we verified this
608 But it guarantees that Blocks are analysed before nodes contained in the
609 block. If so, we can set the value to undef if the block is not \
611 if (is_cfop(n) || is_fragile_op(n) || get_irn_op(n) == op_Start)
619 /* Test for legal loop header: Block, Phi, ... */
620 static INLINE int is_possible_loop_head(ir_node *n) {
621 ir_op *op = get_irn_op(n);
622 return ((op == op_Block) ||
624 ((op == op_Filter) && get_interprocedural_view()));
627 /* Returns non-zero if n is a loop header, i.e., it is a Block, Phi
628 or Filter node and has predecessors within the loop and out
630 @arg root: only needed for assertion. */
632 is_head (ir_node *n, ir_node *root)
635 int some_outof_loop = 0, some_in_loop = 0;
637 /* Test for legal loop header: Block, Phi, ... */
638 if (!is_possible_loop_head(n))
641 if (!is_outermost_Start(n)) {
642 arity = get_irn_arity(n);
643 for (i = get_start_index(n); i < arity; i++) {
644 ir_node *pred = get_irn_n(n, i);
646 if (is_backedge(n, i)) continue;
647 if (!irn_is_in_stack(pred)) {
650 if(get_irn_uplink(pred) < get_irn_uplink(root)) {
651 assert(get_irn_uplink(pred) >= get_irn_uplink(root));
657 return some_outof_loop && some_in_loop;
661 * Returns non-zero if n is possible loop head of an endless loop.
662 * I.e., it is a Block, Phi or Filter node and has only predecessors
664 * @param root: only needed for assertion.
667 is_endless_head (ir_node *n, ir_node *root)
670 int some_outof_loop = 0, some_in_loop = 0;
672 /* Test for legal loop header: Block, Phi, ... */
673 if (!is_possible_loop_head(n))
676 if (!is_outermost_Start(n)) {
677 arity = get_irn_arity(n);
678 for (i = get_start_index(n); i < arity; i++) {
679 ir_node *pred = get_irn_n(n, i);
681 if (is_backedge(n, i)) { continue; }
682 if (!irn_is_in_stack(pred)) {
683 some_outof_loop = 1; //printf(" some out of loop ");
685 if(get_irn_uplink(pred) < get_irn_uplink(root)) {
686 assert(get_irn_uplink(pred) >= get_irn_uplink(root));
692 return !some_outof_loop && some_in_loop;
695 /* Returns index of the predecessor with the smallest dfn number
696 greater-equal than limit. */
698 smallest_dfn_pred (ir_node *n, int limit)
700 int i, index = -2, min = -1;
702 if (!is_outermost_Start(n)) {
703 int arity = get_irn_arity(n);
704 for (i = get_start_index(n); i < arity; i++) {
705 ir_node *pred = get_irn_n(n, i);
707 if (is_backedge(n, i) || !irn_is_in_stack(pred)) continue;
708 if (get_irn_dfn(pred) >= limit && (min == -1 || get_irn_dfn(pred) < min)) {
710 min = get_irn_dfn(pred);
717 /* Returns index of the predecessor with the largest dfn number. */
719 largest_dfn_pred (ir_node *n)
721 int i, index = -2, max = -1;
723 if (!is_outermost_Start(n)) {
724 int arity = get_irn_arity(n);
725 for (i = get_start_index(n); i < arity; i++) {
726 ir_node *pred = get_irn_n(n, i);
727 if (is_backedge (n, i) || !irn_is_in_stack(pred)) continue;
728 if (get_irn_dfn(pred) > max) {
730 max = get_irn_dfn(pred);
737 /** Searches the stack for possible loop heads. Tests these for backedges.
738 If it finds a head with an unmarked backedge it marks this edge and
739 returns the tail of the loop.
740 If it finds no backedge returns NULL.
741 ("disable_backedge" in fiasco)
743 * @param n A node where uplink == dfn.
747 find_tail (ir_node *n) {
749 int i, res_index = -2;
752 if (!icfg && rm_cyclic_phis && remove_cyclic_phis (n)) return NULL;
754 m = stack[tos-1]; /* tos = top of stack */
755 if (is_head (m, n)) {
756 res_index = smallest_dfn_pred(m, 0);
757 if ((res_index == -2) && /* no smallest dfn pred found. */
761 if (m == n) return NULL; // Is this to catch Phi - self loops?
762 for (i = tos-2; i >= 0; --i) {
765 if (is_head (m, n)) {
766 res_index = smallest_dfn_pred (m, get_irn_dfn(m) + 1);
767 if (res_index == -2) /* no smallest dfn pred found. */
768 res_index = largest_dfn_pred (m);
770 if ((m == n) && (res_index == -2)) { /* dont walk past loop head. */
776 /* We should not walk past our selves on the stack: The upcoming nodes
777 are not in this loop. We assume a loop not reachable from Start. */
786 /* A dead loop not reachable from Start. */
787 for (i = tos-2; i >= 0; --i) {
789 if (is_endless_head (m, n)) {
790 res_index = smallest_dfn_pred (m, get_irn_dfn(m) + 1);
791 if (res_index == -2) /* no smallest dfn pred found. */
792 res_index = largest_dfn_pred (m);
795 if (m == n) { break; } /* It's not an unreachable loop, either. */
797 //assert(0 && "no head found on stack");
801 if (res_index <= -2) {
802 /* It's a completely bad loop: without Phi/Block nodes that can
803 be a head. I.e., the code is "dying". We break the loop by
804 setting Bad nodes. */
805 int arity = get_irn_arity(n);
806 for (i = -1; i < arity; ++i) {
807 set_irn_n(n, i, get_irg_bad(get_irn_irg(n)));
811 assert (res_index > -2);
813 set_backedge (m, res_index);
814 return is_outermost_Start(n) ? NULL : get_irn_n(m, res_index);
818 #if EXPERIMENTAL_LOOP_TREE
820 /* ----------------------------------------------------------------
821 AS: This is experimental code to build loop trees suitable for
822 the heap analysis. Does not work correctly right now... :-(
825 Search in stack for the corresponding first Call-End-ProjX that
826 corresponds to one of the control flow predecessors of the given
827 block, that is the possible callers.
828 returns: the control predecessor to chose\
829 or -1 if no corresponding Call-End-Node could be found
831 - -------------------------------------------------------------- */
833 int search_endproj_in_stack(ir_node *start_block)
836 assert(is_Block(start_block));
837 for(i = tos - 1; i >= 0; --i)
839 if(get_irn_op(stack[i]) == op_Proj && get_irn_mode(stack[i]) == mode_X &&
840 get_irn_op(get_irn_n(stack[i], 0)) == op_EndReg)
842 printf("FOUND PROJ!!!!!!!!!!!!!!!!!!!!!!!!!!\n");
843 ir_node *end_projx = stack[i];
845 int arity = get_irn_arity(start_block);
846 for(j = 0; j < arity; j++)
848 ir_node *begin_projx = get_Block_cfgpred(get_irg_start_block(get_irn_irg(end_projx)),
849 get_Proj_proj(end_projx));
850 if(get_irn_n(start_block, j) == begin_projx)
852 printf("FOUND IT!!!!!!!!!!!!!!!!!!\n");
862 static pmap *projx_link = NULL;
864 void link_to_reg_end (ir_node *n, void *env) {
865 if(get_irn_op(n) == op_Proj &&
866 get_irn_mode(n) == mode_X &&
867 get_irn_op(get_irn_n(n, 0)) == op_EndReg) {
868 /* Reg End Projx -> Find the CallBegin Projx and hash it */
869 ir_node *end_projx = n;
870 ir_node *begin_projx = get_Block_cfgpred(get_irg_start_block(get_irn_irg(end_projx)),
871 get_Proj_proj(end_projx));
872 set_projx_link(begin_projx, end_projx);
876 void set_projx_link(ir_node *cb_projx, ir_node *end_projx)
878 if(projx_link == NULL)
879 projx_link = pmap_create();
880 pmap_insert(projx_link, (void *)cb_projx, (void *)end_projx);
883 ir_node *get_projx_link(ir_node *cb_projx)
885 return((ir_node *) pmap_get(projx_link, (void *)cb_projx));
891 is_outermost_loop(ir_loop *l) {
892 return l == get_loop_outer_loop(l);
896 /*-----------------------------------------------------------*
897 * The core algorithm. *
898 *-----------------------------------------------------------*/
900 static void scc (ir_node *n) {
902 if (irn_visited(n)) return;
905 /* Initialize the node */
906 set_irn_dfn(n, current_dfn); /* Depth first number for this node */
907 set_irn_uplink(n, current_dfn); /* ... is default uplink. */
908 set_irn_loop(n, NULL);
912 /* AS: get_start_index might return -1 for Control Flow Nodes, and thus a negative
913 array index would be passed to is_backedge(). But CFG Nodes dont't have a backedge array,
914 so is_backedge does not access array[-1] but correctly returns false! */
916 if (!is_outermost_Start(n)) {
917 int arity = get_irn_arity(n);
919 for (i = get_start_index(n); i < arity; i++) {
921 if (is_backedge(n, i)) continue;
922 m = get_irn_n(n, i); /* get_irn_ip_pred(n, i); */
923 /* if ((!m) || (get_irn_op(m) == op_Unknown)) continue; */
925 if (irn_is_in_stack(m)) {
926 /* Uplink of m is smaller if n->m is a backedge.
927 Propagate the uplink to mark the loop. */
928 if (get_irn_uplink(m) < get_irn_uplink(n))
929 set_irn_uplink(n, get_irn_uplink(m));
934 if (get_irn_dfn(n) == get_irn_uplink(n)) {
935 /* This condition holds for
936 1) the node with the incoming backedge.
937 That is: We found a loop!
938 2) Straight line code, because no uplink has been propagated, so the
939 uplink still is the same as the dfn.
941 But n might not be a proper loop head for the analysis. Proper loop
942 heads are Block and Phi nodes. find_tail searches the stack for
943 Block's and Phi's and takes those nodes as loop heads for the current
944 loop instead and marks the incoming edge as backedge. */
946 ir_node *tail = find_tail(n);
948 /* We have a loop, that is no straight line code,
949 because we found a loop head!
950 Next actions: Open a new loop on the loop tree and
951 try to find inner loops */
953 #if NO_LOOPS_WITHOUT_HEAD
954 /* This is an adaption of the algorithm from fiasco / optscc to
955 * avoid loops without Block or Phi as first node. This should
956 * severely reduce the number of evaluations of nodes to detect
957 * a fixpoint in the heap analysis.
958 * Further it avoids loops without firm nodes that cause errors
959 * in the heap analyses.
960 * But attention: don't do it for the outermost loop: This loop
961 * is not iterated. A first block can be a loop head in case of
962 * an endless recursion. */
966 if ((get_loop_n_elements(current_loop) > 0) || (is_outermost_loop(current_loop))) {
974 ir_loop *l = new_loop();
977 /* Remove the loop from the stack ... */
978 pop_scc_unmark_visit (n);
980 /* The current backedge has been marked, that is temporarily eliminated,
981 by find tail. Start the scc algorithm
982 anew on the subgraph that is left (the current loop without the backedge)
983 in order to find more inner loops. */
986 assert (irn_visited(n));
987 #if NO_LOOPS_WITHOUT_HEAD
994 /* No loop head was found, that is we have straightline code.
995 Pop all nodes from the stack to the current loop. */
1001 static void my_scc (ir_node *n) {
1003 if (irn_visited(n)) return;
1004 mark_irn_visited(n);
1006 /* Initialize the node */
1007 set_irn_dfn(n, current_dfn); /* Depth first number for this node */
1008 set_irn_uplink(n, current_dfn); /* ... is default uplink. */
1009 set_irn_loop(n, NULL);
1013 /* AS: get_start_index might return -1 for Control Flow Nodes, and thus a negative
1014 array index would be passed to is_backedge(). But CFG Nodes dont't have a backedge array,
1015 so is_backedge does not access array[-1] but correctly returns false! */
1017 if (!is_outermost_Start(n)) {
1018 int arity = get_irn_arity(n);
1020 for (i = get_start_index(n); i < arity; i++) {
1022 if (is_backedge(n, i)) continue;
1023 m = get_irn_n(n, i); /* get_irn_ip_pred(n, i); */
1024 /* if ((!m) || (get_irn_op(m) == op_Unknown)) continue; */
1026 if (irn_is_in_stack(m)) {
1027 /* Uplink of m is smaller if n->m is a backedge.
1028 Propagate the uplink to mark the loop. */
1029 if (get_irn_uplink(m) < get_irn_uplink(n))
1030 set_irn_uplink(n, get_irn_uplink(m));
1035 if (get_irn_dfn(n) == get_irn_uplink(n)) {
1036 /* This condition holds for
1037 1) the node with the incoming backedge.
1038 That is: We found a loop!
1039 2) Straight line code, because no uplink has been propagated, so the
1040 uplink still is the same as the dfn.
1042 But n might not be a proper loop head for the analysis. Proper loop
1043 heads are Block and Phi nodes. find_tail searches the stack for
1044 Block's and Phi's and takes those nodes as loop heads for the current
1045 loop instead and marks the incoming edge as backedge. */
1047 ir_node *tail = find_tail(n);
1049 /* We have a loop, that is no straight line code,
1050 because we found a loop head!
1051 Next actions: Open a new loop on the loop tree and
1052 try to find inner loops */
1054 #if NO_LOOPS_WITHOUT_HEAD
1055 /* This is an adaption of the algorithm from fiasco / optscc to
1056 * avoid loops without Block or Phi as first node. This should
1057 * severely reduce the number of evaluations of nodes to detect
1058 * a fixpoint in the heap analysis.
1059 * Further it avoids loops without firm nodes that cause errors
1060 * in the heap analyses. */
1064 if ((get_loop_n_elements(current_loop) > 0) || (is_outermost_loop(current_loop))) {
1072 ir_loop *l = new_loop();
1075 /* Remove the loop from the stack ... */
1076 pop_scc_unmark_visit (n);
1078 /* The current backedge has been marked, that is temporarily eliminated,
1079 by find tail. Start the scc algorithm
1080 anew on the subgraph that is left (the current loop without the backedge)
1081 in order to find more inner loops. */
1084 assert (irn_visited(n));
1085 #if NO_LOOPS_WITHOUT_HEAD
1092 /* No loop head was found, that is we have straightline code.
1093 Pop all nodes from the stack to the current loop. */
1099 /* Constructs backedge information for irg. In interprocedural view constructs
1100 backedges for all methods called by irg, too. */
1101 int construct_backedges(ir_graph *irg) {
1102 ir_graph *rem = current_ir_graph;
1105 assert(!get_interprocedural_view() &&
1106 "not implemented, use construct_ip_backedges");
1109 current_ir_graph = irg;
1110 outermost_ir_graph = irg;
1112 init_scc(current_ir_graph);
1114 current_loop = NULL;
1115 new_loop(); /* sets current_loop */
1116 head_rem = current_loop; /* Just for assertion */
1118 inc_irg_visited(current_ir_graph);
1120 scc(get_irg_end(current_ir_graph));
1122 assert(head_rem == current_loop);
1123 set_irg_loop(current_ir_graph, current_loop);
1124 set_irg_loopinfo_state(current_ir_graph, loopinfo_consistent);
1125 assert(get_irg_loop(current_ir_graph)->kind == k_ir_loop);
1127 irg->loops = current_loop;
1131 count_loop (the_loop, &count, &depth);
1135 current_ir_graph = rem;
1137 return max_loop_depth;
1141 int construct_ip_backedges (void) {
1142 ir_graph *rem = current_ir_graph;
1143 int rem_ipv = get_interprocedural_view();
1147 assert(get_irp_ip_view_state() == ip_view_valid);
1149 outermost_ir_graph = get_irp_main_irg();
1153 current_loop = NULL;
1154 new_loop(); /* sets current_loop */
1155 set_interprocedural_view(1);
1157 inc_max_irg_visited();
1158 for (i = 0; i < get_irp_n_irgs(); i++)
1159 set_irg_visited(get_irp_irg(i), get_max_irg_visited());
1161 /** We have to start the walk at the same nodes as cg_walk. **/
1162 /* Walk starting at unreachable procedures. Only these
1163 * have End blocks visible in interprocedural view. */
1164 for (i = 0; i < get_irp_n_irgs(); i++) {
1166 current_ir_graph = get_irp_irg(i);
1168 sb = get_irg_start_block(current_ir_graph);
1170 if ((get_Block_n_cfgpreds(sb) > 1) ||
1171 (get_nodes_block(get_Block_cfgpred(sb, 0)) != sb)) continue;
1173 scc(get_irg_end(current_ir_graph));
1176 /* Check whether we walked all procedures: there could be procedures
1177 with cyclic calls but no call from the outside. */
1178 for (i = 0; i < get_irp_n_irgs(); i++) {
1180 current_ir_graph = get_irp_irg(i);
1182 /* Test start block: if inner procedure end and end block are not
1183 * visible and therefore not marked. */
1184 sb = get_irg_start_block(current_ir_graph);
1185 if (get_irn_visited(sb) < get_irg_visited(current_ir_graph)) scc(sb);
1188 /* Walk all endless loops in inner procedures.
1189 * We recognize an inner procedure if the End node is not visited. */
1190 for (i = 0; i < get_irp_n_irgs(); i++) {
1192 current_ir_graph = get_irp_irg(i);
1194 e = get_irg_end(current_ir_graph);
1195 if (get_irn_visited(e) < get_irg_visited(current_ir_graph)) {
1197 /* Don't visit the End node. */
1198 for (j = 0; j < get_End_n_keepalives(e); j++) scc(get_End_keepalive(e, j));
1202 set_irg_loop(outermost_ir_graph, current_loop);
1203 set_irg_loopinfo_state(current_ir_graph, loopinfo_ip_consistent);
1204 assert(get_irg_loop(outermost_ir_graph)->kind == k_ir_loop);
1206 current_ir_graph = rem;
1207 set_interprocedural_view(rem_ipv);
1208 return max_loop_depth;
1211 void my_construct_ip_backedges (void) {
1212 ir_graph *rem = current_ir_graph;
1213 int rem_ipv = get_interprocedural_view();
1216 assert(get_irp_ip_view_state() == ip_view_valid);
1218 outermost_ir_graph = get_irp_main_irg();
1222 current_loop = NULL;
1223 new_loop(); /* sets current_loop */
1224 set_interprocedural_view(1);
1226 inc_max_irg_visited();
1227 for (i = 0; i < get_irp_n_irgs(); i++)
1228 set_irg_visited(get_irp_irg(i), get_max_irg_visited());
1230 /** We have to start the walk at the same nodes as cg_walk. **/
1231 /* Walk starting at unreachable procedures. Only these
1232 * have End blocks visible in interprocedural view. */
1233 for (i = 0; i < get_irp_n_irgs(); i++) {
1235 current_ir_graph = get_irp_irg(i);
1237 sb = get_irg_start_block(current_ir_graph);
1239 if ((get_Block_n_cfgpreds(sb) > 1) ||
1240 (get_nodes_block(get_Block_cfgpred(sb, 0)) != sb)) continue;
1242 my_scc(get_irg_end(current_ir_graph));
1245 /* Check whether we walked all procedures: there could be procedures
1246 with cyclic calls but no call from the outside. */
1247 for (i = 0; i < get_irp_n_irgs(); i++) {
1249 current_ir_graph = get_irp_irg(i);
1251 /* Test start block: if inner procedure end and end block are not
1252 * visible and therefore not marked. */
1253 sb = get_irg_start_block(current_ir_graph);
1254 if (get_irn_visited(sb) < get_irg_visited(current_ir_graph)) scc(sb);
1257 /* Walk all endless loops in inner procedures.
1258 * We recognize an inner procedure if the End node is not visited. */
1259 for (i = 0; i < get_irp_n_irgs(); i++) {
1261 current_ir_graph = get_irp_irg(i);
1263 e = get_irg_end(current_ir_graph);
1264 if (get_irn_visited(e) < get_irg_visited(current_ir_graph)) {
1266 /* Don't visit the End node. */
1267 for (j = 0; j < get_End_n_keepalives(e); j++) scc(get_End_keepalive(e, j));
1271 set_irg_loop(outermost_ir_graph, current_loop);
1272 set_irg_loopinfo_state(current_ir_graph, loopinfo_ip_consistent);
1273 assert(get_irg_loop(outermost_ir_graph)->kind == k_ir_loop);
1275 current_ir_graph = rem;
1276 set_interprocedural_view(rem_ipv);
1279 static void reset_backedges(ir_node *n) {
1280 if (is_possible_loop_head(n)) {
1281 int rem = get_interprocedural_view();
1283 set_interprocedural_view(1);
1285 set_interprocedural_view(1);
1287 set_interprocedural_view(rem);
1293 static void loop_reset_backedges(ir_loop *l) {
1295 reset_backedges(get_loop_node(l, 0));
1296 for (i = 0; i < get_loop_n_nodes(l); ++i)
1297 set_irn_loop(get_loop_node(l, i), NULL);
1298 for (i = 0; i < get_loop_n_sons(l); ++i) {
1299 loop_reset_backedges(get_loop_son(l, i));
1304 static void loop_reset_node(ir_node *n, void *env) {
1305 set_irn_loop(n, NULL);
1310 /** Removes all loop information.
1311 Resets all backedges */
1312 void free_loop_information(ir_graph *irg) {
1313 /* We can not use this recursion, as the loop might contain
1314 illegal nodes by now. Why else would we throw away the
1316 if (get_irg_loop(irg)) loop_reset_backedges(get_irg_loop(irg));
1318 irg_walk_graph(irg, loop_reset_node, NULL, NULL);
1319 set_irg_loop(irg, NULL);
1320 set_irg_loopinfo_state(current_ir_graph, loopinfo_none);
1321 /* We cannot free the loop nodes, they are on the obstack. */
1325 void free_all_loop_information (void) {
1327 int rem = get_interprocedural_view();
1328 set_interprocedural_view(1); /* To visit all filter nodes */
1329 for (i = 0; i < get_irp_n_irgs(); i++) {
1330 free_loop_information(get_irp_irg(i));
1332 set_interprocedural_view(rem);
1339 /* Debug stuff *************************************************/
1341 static int test_loop_node(ir_loop *l) {
1342 int i, has_node = 0, found_problem = 0;
1345 assert(l && l->kind == k_ir_loop);
1347 if (get_loop_n_elements(l) == 0) {
1349 dump_loop(l, "-ha");
1352 le = get_loop_element(l, 0);
1353 if (*(le.kind) != k_ir_node) {
1354 assert(le.kind && *(le.kind) == k_ir_loop);
1357 dump_loop(l, "-ha");
1360 if ((*(le.kind) == k_ir_node) && !is_possible_loop_head(le.node)) {
1362 dump_loop(l, "-ha");
1365 if ((get_loop_depth(l) != 0) &&
1366 (*(le.kind) == k_ir_node) && !has_backedges(le.node)) {
1368 dump_loop(l, "-ha");
1373 for (i = 0; i < get_loop_n_elements(l); ++i) {
1374 le = get_loop_element(l, i);
1375 if (*(le.kind) == k_ir_node)
1378 if (test_loop_node(le.son)) found_problem = 1;
1381 if (has_node == 0) {
1383 dump_loop(l, "-ha");
1386 return found_problem;
1389 /** Prints all loop nodes that
1390 * - do not have any firm nodes, only loop sons
1391 * - the header is not a Phi, Block or Filter.
1393 void find_strange_loop_nodes(ir_loop *l) {
1394 int found_problem = 0;
1395 found_problem = test_loop_node(l);
1396 printf("Finished Test\n\n");
1397 if (found_problem) exit(0);
1401 /* ------------------------------------------------------------------- */
1402 /* Simple analyses based on the loop information */
1403 /* ------------------------------------------------------------------- */
1405 int is_loop_variant(ir_loop *l, ir_loop *b) {
1408 if (l == b) return 1;
1410 n_elems = get_loop_n_elements(l);
1411 for (i = 0; i < n_elems; ++i) {
1412 loop_element e = get_loop_element(l, i);
1413 if (is_ir_loop(e.kind))
1414 if (is_loop_variant(e.son, b))
1421 /* Test whether a value is loop invariant.
1423 * @param n The node to be tested.
1424 * @param block A block node. We pass the block, not the loop as we must
1425 * start off with a block loop to find all proper uses.
1427 * Returns non-zero, if the node n is not changed in the loop block
1428 * belongs to or in inner loops of this blocks loop. */
1429 int is_loop_invariant(ir_node *n, ir_node *block) {
1430 ir_loop *l = get_irn_loop(block);
1431 ir_node *b = (is_Block(n)) ? n : get_nodes_block(n);
1432 return !is_loop_variant(l, get_irn_loop(b));